This invention relates to electronic compositions, and more particularly to compositions comprising novel vehicles.
The use of a volatile organic liquid viscosified by a polymeric component dissolved therein as a medium or vehicle for dispersing finely divided inorganic powders (e.g., less than 200 mesh, standard U.S. sieve scale) and then printing the dispersion on dielectric substrates, is well known in the electronics art. The printed substrate is then heated or fired to first remove the vehicle from the printed pattern and then sinter or cure the inorganic powders into the desired function (e.g., resistors, conductors, dielectrics, varistors, etc.) adherent to the substrate. Materials and their propertions, as well as printing and firing techniques and conditions, are well known to those skilled in the electronics art. Typical of the vehicles employed are those of Short U.S. Pat. No. 3,536,508, issued Oct. 27, 1970, and incorporated by reference herein. Vehicles comprising solvents such as terpineol or butyl carbitol (C.sub.4 H.sub.9 OCH.sub.2 CH.sub.2 OH) have been commercially available for several years, but improved vehicles are required.
There has developed a need for vehicles which are characterized by decreased sensitivity of viscosity to variations in ambient temperature, so that dispersions or inorganic materials in such vehicles exhibit such decreased sensitivity of viscosity. Decreased sensitivity to temperature would lead to more reproducible print thickness and hence more reproducible electronic functions (e.g., resistors). Furthermore, after the dispersion has been printed on a substrate in the desired pattern and before it is fired, the ambient temperature may change and/or the printed substrate may be exposed to variations in temperature as it proceeds from one work station to another prior to firing. Especially desired would be a vehicle system which is capable of forming dispersions which exhibit less than a 40% change in viscosity when the temperature is changed from 20.degree. to 30.degree. C.
Also needed are vehicles which are less hygroscopic than conventional vehicles, and also tend to be less reactive with the inorganic solids.